Investment Securities (Schedule Of Contractual Maturities Of Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012
Available for sale, Under 1 Year	$ 7,250
Available for sale, 1 to 5 Years	32,276
Available for sale, 6 to 10 Years	27,544
Available for sale, Over 10 Years	36,841
Held to maturity, Under 1 Year	1,530
Held to maturity, 1 to 5 Years	2,216
Held to maturity, 6 to 10 Years	378
Held to maturity, Over 10 Years	4,544
Student Loans [Member]
Available for sale, Under 1 Year	142
Available for sale, 1 to 5 Years	5,607
Available for sale, 6 to 10 Years	7,552
Available for sale, Over 10 Years	3,466
Credit Cards [Member]
Available for sale, Under 1 Year	1,528
Available for sale, 1 to 5 Years	6,980
Available for sale, 6 to 10 Years	1,702
Available for sale, Over 10 Years	0
Sub-Prime [Member]
Available for sale, Under 1 Year	324
Available for sale, 1 to 5 Years	50
Available for sale, 6 to 10 Years	9
Available for sale, Over 10 Years	996
Other Asset-Backed Securities [Member]
Available for sale, Under 1 Year	114
Available for sale, 1 to 5 Years	2,039
Available for sale, 6 to 10 Years	1,288
Available for sale, Over 10 Years	238
Asset-Backed Securities [Member]
Available for sale, Under 1 Year	2,108
Available for sale, 1 to 5 Years	14,676
Available for sale, 6 to 10 Years	10,551
Available for sale, Over 10 Years	4,700
State And Political Subdivisions [Member]
Available for sale, Under 1 Year	500
Available for sale, 1 to 5 Years	3,014
Available for sale, 6 to 10 Years	2,812
Available for sale, Over 10 Years	862
Held to maturity, Under 1 Year	49
Held to maturity, 1 to 5 Years	40
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	0
Collateralized Mortgage Obligations [Member]
Available for sale, Under 1 Year	69
Available for sale, 1 to 5 Years	2,166
Available for sale, 6 to 10 Years	593
Available for sale, Over 10 Years	1,451
Held to maturity, Under 1 Year	276
Held to maturity, 1 to 5 Years	1,563
Held to maturity, 6 to 10 Years	184
Held to maturity, Over 10 Years	1,018
Other U.S. Debt Securities [Member]
Available for sale, Under 1 Year	283
Available for sale, 1 to 5 Years	2,855
Available for sale, 6 to 10 Years	874
Available for sale, Over 10 Years	39
U.S. Treasury And Federal Agencies [Member] | Direct Obligations [Member]
Available for sale, Under 1 Year	200
Available for sale, 1 to 5 Years	75
Available for sale, 6 to 10 Years	662
Available for sale, Over 10 Years	787
U.S. Treasury And Federal Agencies [Member] | Mortgage-Backed Securities [Member]
Available for sale, Under 1 Year	5
Available for sale, 1 to 5 Years	1,723
Available for sale, 6 to 10 Years	9,926
Available for sale, Over 10 Years	21,063
Held to maturity, 1 to 5 Years	48
Held to maturity, 6 to 10 Years	58
Held to maturity, Over 10 Years	129
U.S. Treasury And Federal Agencies [Member] | Asset-Backed Securities [Member]
Held to maturity, 1 to 5 Years	0
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	25
Non-U.S. Debt Securities [Member]
Available for sale, Under 1 Year	4,085
Available for sale, 1 to 5 Years	7,767
Available for sale, 6 to 10 Years	2,126
Available for sale, Over 10 Years	7,939
Held to maturity, Under 1 Year	1,205
Held to maturity, 1 to 5 Years	565
Held to maturity, 6 to 10 Years	136
Held to maturity, Over 10 Years	3,372
Non-U.S. Debt Securities [Member] | Mortgage-Backed Securities [Member]
Available for sale, Under 1 Year	477
Available for sale, 1 to 5 Years	3,195
Available for sale, 6 to 10 Years	420
Available for sale, Over 10 Years	7,479
Held to maturity, Under 1 Year	1,202
Held to maturity, 1 to 5 Years	102
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	3,356
Non-U.S. Debt Securities [Member] | Asset-Backed Securities [Member]
Available for sale, Under 1 Year	255
Available for sale, 1 to 5 Years	2,668
Available for sale, 6 to 10 Years	1,577
Available for sale, Over 10 Years	460
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	303
Held to maturity, 6 to 10 Years	136
Held to maturity, Over 10 Years	0
Non-U.S. Debt Securities [Member] | Government Securities [Member]
Available for sale, Under 1 Year	1,703
Available for sale, 1 to 5 Years	0
Available for sale, 6 to 10 Years	0
Available for sale, Over 10 Years	0
Held to maturity, Under 1 Year	3
Held to maturity, 1 to 5 Years	0
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	0
Non-U.S. Debt Securities [Member] | Other Non-U.S. Debt Securities [Member]
Available for sale, Under 1 Year	1,650
Available for sale, 1 to 5 Years	1,904
Available for sale, 6 to 10 Years	129
Available for sale, Over 10 Years	0
Held to maturity, Under 1 Year	0
Held to maturity, 1 to 5 Years	160
Held to maturity, 6 to 10 Years	0
Held to maturity, Over 10 Years	$ 16